Gas-tight seal and terminal for electric furnaces



March 16, 1948.

J. G. HOOP 2,438,008

GAS-TIGHT SEAL AND TERMINAL FOR ELECTRIC FURNACES Filed Jan. l2, 1946 ATTORNEY Patented Mar. 16, 1948 GAS-TIGHT SEAL AND TERMINAL FOR ELECTRIC FURNACES .lohn G. Hoop,

Pittsburgh, Pa., assigner to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application llarulary 12, 1946, Serial No. 640,783

3 Claims. l

This invention is directed to providing a gastight terminal structure through which electricity is passed for heating or other purposes. The invention is an improvement over that shown and claimed in the Lessmann Patent No. 2,200,115 of May 7, 194i), in which a structure is disclosed for sealing a hole in a furnace wall through which a terminal conductor passes. The structure comprises two asbestos boards or blocks which have conical grooves aligned with the hole. Gaskets are provided between the boards and the furnace wall, and the conical grooves are filled with packing. The boards are specially arranged between a plurality of bolts and two rigid metal plates. By tightening nuts on the bolts, the boards are gas-tightly sealed against the furnace wall and the packing is compressed around the conductor, for preventing gas leakage through the aforesaid hole.

The primary purpose of this invention is to improve and simplify such a structure so that it can be more easily constructed, will have a longer life, and will permit easier servicing when necessary,

Objects, features and innovations of my inventon will be apparent or discernible from the following description of a preferred embodiment. rihe description is to be taken in conjunction with the accompanying drawing, not to scale, in which:

Figure l is a sectional view through a terminal structure embodying my invention, showingthe furnace with whz ch it is associated only schematically;

Fig. 2 is a broadside view of one of the asbestos boards used in the terminal structure;

Fig. 3 is a broadside view of a second board used in the terminal structure;

Fig. 4 is an enlarged sectional view taken on the line lV-IV of Fig. 3, and

Eig. 5 is a broadside view of gaskets used in the terminal structure.

My invention is particularly applicable to an industrial heat-treating furnace having a heating chamber in which a charge is enveloped, during heat-treatment, by a special controlled or inert atmosphere, Such a furnace is usually gastight in order to minimize loss of atmosphere and to prevent innltration of air which might cause damage to the charge, Generally, a furnace of this type has an outer gas-tight metal casing through which pass the terminals for the electrical heating units inside of the furnace,

In Fig. l, a fragmentary wall-portion l represents the outer metal casing and brick of an `in- (Cl. Hel- 151) dustrial or other similar furnace. The wall-portion l has a plurality of holes 2 through which pass parallel terminal conductors 3 spaced apart in accordance with the voltage between them. The holes 2 are oversize to provide adequate electrical insulation between the metal wall of the outer casing of the furnace and the respective conductors. Each of the conductors 3 comprises a round rod having a smooth inner portion i and a threaded outer end-portion 5. A plurality of contact nuts E are usually provided on the threaded part of each conductor for securing cables l through which power is supplied to heating elements 3 connected te the other inner ends of the terminal conductors; the heating elements being represented schematically.

For holding the conductors 3 centraly in the holes i', and gas-tightly sealing these holes, a seal is provided. accordance with the preferred embodiment of my invention, such a seal comprises a plurality of bolts 9 which pass through the casing of the wall-portion at corners of a rectangle encompassing the holes 2, and at midpoints of those sides of the rectangle which span the conductors 3. The bolts have heads welded or otherwise gas-tightly secured to the inner side of the casing of the wall-portion l, with the bodies of the bolts extending outwardly from the furnace wall,

Assembled on the bolts, in a direction outwardly from the wall-portion I, are one or more gaskets I0, a supporting or reinforcing heat-resistant electricity-insulating board il, another gasket I 2, and a second heat-resistant electricityinsulating board I3. The boards are preferably of asbestos lumber and the gaskets of asbestos paper. Each of the parts is provided with a plurality of peripheral holes lll adapted to slidably receive the bolts 9, and with a plurality of spaced central holes through which the terminal conductors 3 can pass. The gaskets l0 and l2 have oversize central holes I5; the inner board Il has central holes I6 which t the conductors fairly snugly but with suiiicient clearance to allow the conductors to be slipped through the holes and to expand; and the outer board I3 has ccntral holes Il which are alike, each comprising several coaxial or counterbored hole portions. A hole-portion I8 is at the inner end of the hole ll and is of a size substantially the same as the aligned hole I6 in the inner board Il. An intermediate hole-portion I9 is tapered outwardly from the outer end of the hole-portion I8 until it meets a cylindrical oversize hole-portion 20. The cylindrical hole-portion 20 is large enough to receive a metal sleeve 23 which slips over a conductor with a snug t. The sleeve 23 extends outwardly beyond the outer board I3 and is pressed inwardly by a pressing nut 24 threaded on the threaded end 5 of a conductor 3, for compressing asbestos packing material 25 in the tapered hole-portion I9, for gas-tightly sealing the space between the conductor and the hole I'I in the board through which the conductor passes.

At the inner face of the board I3, a pair Vof relatively elongated grooves 26 extend from opposite sides of each smaller cylindrical hole-portion I8, for receiving a pin 21 which passes loosely through a hole in the associated conductor. When the pressing nut- 25 is tightened forv compressing the packing 25, the associated pin 21 is pulled against the outer board I3, so that the pinV not only prevents rotation of the associated conductor during tightening of the nuts on the con;

ductor, but also prevents excessive longitudinal movement of the conductor in either direction.

In assembly, the gaskets IQ and the inner board II are slipped over the bolts 9 and conductors 3. The pins 21 `are slipped through the conductors and then the gasket I2 and board I3 put in place. The boards and gaskets are gas-tightlyrpressed against the wall-portion I by means ofv nuts 28 on the outer ends of the bolts 9, the nuts bearing on intermediate Washers 29 for spreading the com pressing force. The packing 25 is then placed in the holes Il, the 4sleeves 23 slipped over the conductors and the nuts 23 applied to fix the conductors securely in position and at the same time compress the packing material. The contact nuts E and cables S can be added at any time after the terminal structure has been assembled. For repacking from time to time, a nut 24 is loosened, the sleeve 23 slid backward, packing added, and then the nut retightened, without disturbing the rest of the terminal structure.

I claim as my invention:

l. A terminal structure primarily for an industrial electric urnace, comprising the combination with a metallic wall-portion for said furnace, a terminal conductor insulatedly passing through a hole in said wall-portion, said conductor having a threaded outer end, and a plurality of spaced bolts; of a plurality of facing insulating boards, each having a central hole, said holes being coaxial, said conductor passing through said coaxial holes, means associated with said bolts, for gas-tightly holding said plurality of boards against said wallpcrtion, a first of said boards having an elongated groove extending from the central hole in said iirstboard, said groove being in a side of said rst board, which is adjacent the second of said boards, a transverse extension associated with said conductor and lying in said groove, said hole having an enlarged portion and packing therein, and means comprising a nut screwed on said threaded end of the conductor for compressing said packing for sealing said hole-means against gas-leakage.

2. A terminal structure primarily for an industrial electric furnace, comprising the combination with a metallic wall-portion for said furnace, a terminal conductor insulatedly passing through a hole in said Wall-portion, said con- ,ductor having a threaded outer end, and a plu ing nut screwed on said threaded ends of the conductors for compressing said packing for sealing said holes against gas-leakage, a first of said boards having an elongated groove extending from its central hole, the groove being in the side of the board, which faces the second of said boards, and a transverse extension for said conductor lying in said groove.

3. A structure including that of claim 2, but characterized further by said compressing means comprising a sleeve-like member at the inner side ci said pressing nut, and by nuts on the threaded end of said conductor spaced from said pressing nut a distance sucient to allow the pressing nut and sleeve-like member to be moved outwardly for providing access for said packing.

JOHN G. HOOP.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Great Britain May 20, 1937 

